Variable ratio transformer



Oct. 13, 1953 B H PUSKE 2,655,636

- VARIABLE RATIO TRANSFORMER Filed Oct. 6, 1950 2 Sheets-Sheet lINVENTbR. 55977904 0 fl P1 ASK/6 ArrveA Oct. 13, 1953 s. H. PLISKE2,655,636

VARIABLE RATIO TRANSFORMER Filed Oct. 6, 1950 2 Sheets-Sheet 2 INVENTOR.55271404 0 6. Pas K6 Arroe/vsy Patented Oct. 13, 1953 UNITED sTATEsPATENT OFFICE VARIABLE RATIO TRANSFORMER Berthold H. Pliske, Cleveland,Ohio, assignor to. The Ohio Crankshaft Company, Cleveland, Qhiaa o rqratq of 01.110

Application October 6, 1950, Serial No. 188,784

2 Claims. 1

This invention pertains to the art of stationary electrical transformersand, more particularly to a variable ratio transformer.

The invention is particularly applicable to high-power transformers ofthe type normally employed in the art of high-frequency inductionheating. In such transformers, all parts must be water cooled to removethe heat generated in the transformer by the flow of currents in thetransformer or by eddy currents induced throughout the transformer. Theinventionwillbe described with reference to such a transformer although,of course, it is not limited to such applications.

Variable ratio transformers, are well known in the transformer art.Normally, the primary or secondary of the transformer, or both, areprovided with a pluralit oftaps and flexible leads are provided whichmay be connected toany one of the taps to give the desired ratio ofpower transformation. In the art to which this invention applies,theuse. offlexible leads toconnect to the desired tap of; thetransformer has been found to be completely impracticable because of thenecessity-forwa-ter cooling the'leads. The water cooling of flexibleleads is a rather diflicult problem. Furthermore, because. of the highcurrents which must be. handled, the leads would have to be of a ratherlarge-gage copper and would be extremely stiffand difficult to bandle.For this reason and prior-to the. present invention, it has beenconventional to construct fixed ratio transformers to the desired ratio;and, if the ratio of electrical transformation had to be changed, anewtransformer with a different turns ratio was substituted.

In accordance. with the present invention, a transformer is comprised ofa multi-turn Watercooled coil having short rigid taps on selected turns.a water-cooled collector bus or buses in close-spaced relationship tothe taps and means for selectively connecting the bus or buses to one ofthe coil taps, these means being relatively short and rigid and cooledby heat conduction to the' Another object of the invention is theprovision of a new and improved variable ratio transformer includingcoils having a plurality of short, rigid taps therealong and a collectorbus in spaced proximity to said taps adapted to be selectively connectedone at a time to said taps, the coil and collector rings being watercooled and the spacing between the collector and taps being sufiicientlysmall that a connector placed between the ring and the taps will becooled by the con duction of heat to both the taps and the collectorrings.

The invention is comprised in certain parts and combination of parts, apreferred embodiment of which will be described in this application andillustrated in the accompanying drawings which are a part hereof, andwherein;

Figure 1 is a side elevatienal view of; a variable ratiotransformerembodying the. present inven ticn,

Figure 2 is a sectional view of Figure 1 taken approximately on the line2 2 thereof, and,

Figure 3 is a fragmentary-sectional.view of. Figure 1- takenapproximately on theline33ither,eof to show in large detail one ofthetaps on the coils and the; collector bus therefor.

Referring-now to the drawingswhereina preferred embodiment of theinvention isshownfor the purposes of illustration only, and notfor thepurposes oflimitation, the figures show a variable ratio transformercomprised of a core A, a tapped coil B and a pair of collector busescadapted to be connected selectively to the, coil taps. The busesare, inturn, adapted tobe connected to bus bars or other power leads (notshown) connecting, in turn, to other electrical apparatus.

The core A is relatively conventional in construction and includesthreelegs [0, H, l2 extending in spaced parallel relationship from anintegral base i 3. A keeper bar l4 extends across the three free ends ofthe legs to complete the magnetic circuit. The core is made up of astack of a plurality of relatively flat and thin laminations formed froma magnetically-permeable material. Theselaminations-are interleaved by aplurality of identically-shapedcooling laminationslfi formed of copperor other highheatconducting material, which have tubes ll brazed orsoldered along edges thereof through which a cooling medium may becirculated. The stack of laminations is sandwiched betweenwoodstrips 20.Steelframe members l8, ofwhichthere are four, overlay. the wood strips20; alongthe length of the outer legs and both-sides thereof. The entirestack of laminations, woodenstripslll and frame members I 8 are held intight assembled relationship by a plurality of transverse bolts I9. Thedimensions of the three legs are such that the center leg it has twicethe cross-sectional area of any one side leg or, in other words, the sumof the cross-sectional area of the two side legs ill, I2 is equal tothat of the center leg 6 l. The invention is, of course, equallyapplicable to any other type of core, including an air core.

The coils B in the embodiment shown comprise primary and secondarywindings 2|, 22 positioned about the center leg I I of the core A. Theprimary winding is comprised of a single layer of a plurality of spacedcontinuous turns formed of an edgewise-bent, flat, rectangular tube ofcopper or the like. These turns are spaced and the secondary turns aredisposed in the space between the primary turns. Each secondary turn iscomprised of a single turn. The ends of the secondary turns extendradially outwardly for a short distance and are brazed or otherwisesuitably jointed to the respective terminal blocks 24 or 25. Thesecondary turns are also formed from edgewise-bent, flat, rectangulartubing.

The primary and secondary windings may be insulated from each other byimpregnating the coils before assembly or by suitable spacer memberspositioned between each turn after assembly. Cooling water is circulatedthrough the hollow interior of the primary through hose fittings 26 in aconventional manner.

The primary winding H has means for making electrical connection toselected turns along its length. These means are generally all similarin construction and reference to Figure 3 1 shows a typicalconstruction. Thus, the means shown comprise a short, flat copper lug orplate 30 edge brazed to the outer edge of the conductor of the primarywinding H at the point where a tap is desired. An L-shaped bracket 3 I,also of copper, is bolted to the lug 38 by a bolt 32. The bracketincludes a vertically extending flange 35 which is provided with athreaded opening 36.

As shown, the taps are spaced axially along the coil and preferablyadjacent taps are spaced circumferentially on the coil but always on thesame side of the core A. To reduce the axial distance between thethreaded openings 35, the bracket 3| associated with the uppermost tapsmay be so positioned that the flange 35 extends downwardly from the lug30, while the brackets associated with the lower taps have the flange 35extending above the respective lug 30.

The invention is equally applicable to multilayered coils or to anautotransformer arrangement of coils. The particular construction oftaps shown may be altered. The construction shown is simple, rigid andeasily adjusted.

The collector bus C comprises rigid watercooled means for makingelectrical connection selectively to the primary taps. In the embodimentshown, the collector buses each comprise a relatively-thin wide strip ofcopper or the like, electrically-conductive material rigidly mounted onthe core A and so formed as to be in closespaced insulated relationshipto the outer radial surfaces of the flanges 35. The buses all haveopenings 38 aligned with the openings 36 through which a bolt may beinserted to connect a desired tap to the bus.

The buses may be supported relative to the coil in any desired waybut,in the embodiment shown, the ends of the collector bus are fastened toan insulating dowel 39 which, in turn, is

threadably supported on a threaded extension 37 of some of the corebolts l9.

Each of the collector buses C has a copper tube to brazed to one edgethereof having hose fitings ll at each end to which suitablewatercooling connections may be made. Other forms of construction of thecollector bus may be employed.

When it is desired to connect the collector bus to one of the taps, acopper washer 43 is positioned in the space between the flange and thecollector bus. This washer has a groove formed in one surface to guidethe washer over the flange 35. The opposite surface of the washer iscurved to match the inner curvature of the collector bus. When thewasher is placed into position, a bolt 44 is inserted through thealigned openings 38 in the collector bus and the washer 43 and thenthreaded into the opening 36 of the flange 35 and tightened downsecurely. With such construction, there is no danger of the collectorbus being in any way deformed so as to electrically engage two taps atone time.

In the transformer shown, it will be seen that all elements thereof aresubject to artificial cool ing. For example, the core is cooled by theheat in the magnetic laminations being conducted to the coolinglaminations and then to the cooling water in the tube. In a like manner,the primary and secondary coils will be cooled by cooling watercirculated through the interior of the tubes. The lugs ill which arebrazed to the primary coil are short in length and artificially cooleddue to the thermal conductivity which will occur from the lug as to thetube H. The collector buses are cooled by the tubes 4!! brazed to theedges thereof. The washers 43 disposed between the collector bus and theflange 35 may be cooled by the conduction of heat both to the collectorbus and through the bracket 3| to the lug 38 and then to the coolingwater in the primary winding.

The transformer described has proven extremely efficient and effectivein practice. All portions through which electrical currents must floware artificially cooled. Changes in the ratio of the transformer may bereadily made without the necessity of moving stiff, flexible leads fromtap to tap simply by positioning a washer between the desired tap andthe collector bus and screwing a bolt through the openings up tight.

The transformer above described illustrates only one embodiment whichthe present invention may take. Obviously, many other constructions andarrangements will occur to others upon a reading and understanding ofthis specification and it is my intention to include all suchmodifications and alterations insofar as they come within the scope ofthe appended claims.

Having thus described my invention, I claim:

1. A variable ratio transformer comprising a core, including a centerleg and a pair of side legs in spaced parallel relationship to and oneon,

side of said center leg; a helical coil formed members extending towardand having surfaces uniformly close spaced from the surface of said busmember facing said coil, said bus member having a plurality of openings,one for each lug member aligned with an opening in the respective lugmember; and a conductor member having a thickness generallycorresponding to the spacing between the lug and bus members adapted obe selectively positioned between one of said ug members and said busmembers, said con- "iuctor member having an opening adapted to bealigned with said lug and bus member openings and means extendingthrough said openings for holding the surfaces of said bus and conductormember and said conductor and lug member in electrically-conductingengagement.

2. A variable ratio transformer comprising a multiturn helical coilformed of a heavy hollow conductor; means for circulating a coolingmedium through the center of said conductor; a bus of a heavy, rigid,conductive material mounted in fixed, spaced, relatively-closerelationship to a side of said coil; means for artificially cooling saidbus; a plurality of conductor lugs fixed to the edges of said coil atpredetermined points spaced axially along said coil and on the sidethereof adjacent said bus, all of said lugs extending toward said busand having surfaces uniformly close spaced from the surface of said busfacing said coil; said bus having a plurality of openings; one for eachlug, aligned with an opening in the respective lug; and a conductormember having a thickness generally corresponding to the spacing betweenthe lug and the bus adapt ed to be selectively positioned between one ofsaid lugs and said bus, said member having an opening adapted to bealigned with said lug and bus opening and means extending through saidopenings for holding the surfaces of said bus and member and said memberand lug in firm counter-conducting engagement.

BERTHOLD H. PLISKE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,325,810 Strickland, Jr. Aug. 3, 1943 2,459,971 Stanton Jan.25, 1949 2,474,395 Early et al June 28, 1949

